Pole-changer switching circuit



Nov. 3,1925- J. F. MEYERS POLE CHANGER SWITCHING CIRCUIT Filed- Oct. 1.192;

ME? I Patented Nov. 3, 1925.

UNITED STATES PATENT OFFICE.

JOHN F. MEYERS, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCHBOARDAND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

POLE-CHANGER SWITCHING CIRCUIT.

Application filed October 1, 1923. Serial No. 685,798.

To ("N 1071071), if may concern.

Be it known that I, Jenn F. Mnrnns, a citizen of the United States ofAmerica, residing in Chicago, county of Cook, and State of Illinois,have invented certain new and useful Improvements in Pole-ChangerSwitching Circuits, of which the following is a specification.

My invention relates to switching circuits and has to do moreparticularly with circuits in which duplicate sets of apparatus areemployed and in which means are provided for automatically switchingfrom one set of apparatus to another. In telephone systems of the classin which pole changers are used for delivering ringing current,duplicate pole clnlnger sets are employed, one of which may be termedthe primary pole changer and the other pole changer may be termed theemergency pole changer. It sometimes happens that the primary polechanger becomes disabled and stops for various reasons such asmechanical trouble, or circuit trouble thus making it necessary toemploy the emergency pole changer. In order to connect this emergencychanger, the operator presses a button which is located on theswitchboard and under her control, or a switch which is located on thepowerboard. This means of connecting and disconnecting the pole changersis objectional because of loss of time and the interruption of ringingcurrent, it being done manually. To overcome'these objectional features,I provide a switching cir-.

cuit which automatically switches from one pole changer to the other.

A. feature of my invention is the provision of a key which when moved toone position, places the primary pole changer in operative circuit andwhen moved to its other position the primary pole changer is cut off andplaces the emergency pole changer in operative circuit so that theprimary pole changer may be used for a period of time and when desirablethis primary pole changer may be shut oil by opening its associated keycontacts, and the moving of the key to its other position will connectthe emergency pole changer in operative circuit for any desired lengthof time. I

Another feature of my invention is the provision of means whereby shouldthe primary pole changer which is #onnccted in pole circuit by means ofits associated key contacts stop for various reasons, such as theopening of a fuse, or mechanical trouble, the said means -will functionautomatically to switch from the primary pole changer to the emergencypole changer without the manipulation of any keys 'or buttons.

Another feature of my invention is the provision of one set oftransformers for the primary and emergency pole changers and automaticmeans which control the switching of the transformers from one polechanger to the other when the switching means operates to switch fromone pole changer to the other.

Referring now in general to my invention as illustrated in theaccompanying drawing, 1 shown a primary pole changer A comprising unitsM and N. The units 'M and N comprise vibrator magnets Vhl and VM andtheir associated vibrator contacts. The pole changer C which I term theemergency pole changer comprises the units 0 and P which consist of thevibrator magnets VM and VM and their associated vibrator contacts. Ishow a transformer T which is common to the units M and O of the polechangers A and C and a transformer T which is common to the units N andP of the pole changers A and C. Retardation coils RC and RC .are alsoprovided, retardation coil RC being common to units M and O of the polechangers A and G and retardation coil RC being common to units N and Pof pole changers A and C. The retardation coils are used for the usualtone purposes. I also provide a pole changer switching relay PR which isassociated with the units M and O of the pole changers A and C and whenoperated switches the transformer T from the unit M of the pole changerA to the unit O of the pole changer C and also switches the retardationcoil RC from unit M to unit 0. A pole changer switching relay PR"accociated with the units N and P of the pole changers A and C whenoperated switches the transformer T from the unit N of pole changer A tounit P of the pole changer C. I also show alternating current relays ACand AC, the relay AC being common to units H and O of pole changers Aand C and relay AC'heing common to units N and P of the pole changers Aand C. An emergency control relay ECP is provided and in associationwith the relays AC and AC the said relays automatically control theswitching from the pole changer A to C or vice versa. 7

I provide a switching key K which is of the usual cam type, and has twopositions a. and 0. lVhen the key is moved to its a position the polechanger A is the pole changer that will be operated when the startingkey SK is moved to its starting position SP and when the key K is movedto its position the pole changer C will be the pole changer that isoperated when the starting key is moved to its starting position SP. Thestarting key SK is also of the usual cam type and has a startingposition SP and an emergency position EP to which it is moved from itsstarting position SP when starting the pole changer A or G as the casemay be for purposes as will be more fully hereinafter described. Iprovide a battery switching key BK of the usual cam type to connecteither the batter B or B for current supply purposes.

I also provide a testing key 'TK associated with the pole changer A fortesting the pole changer A and a testing key TX for testing the polechanger C.

Having described in general the apparatus comprising my invention, Iwill now describe in detail'the operation of the switching circuit of myinvention.

Assuming that the primary pole changer A is the pole changer being used,its associated key switch K is moved to its position (L and furtherassuming that the battery B is being-used, its associated battery switching key BK will be in its actuated position. To startthe pole changer A,starting key switch SK is moved to its. starting position SP to close acircuit for the vibrator inagnets VM and VM of. the units Mfa'nd N ofthe pole changer A, the circuit of vibrator magnet VM- being traced frombattery B, over conductor 2, closed contacts 3 an (1 4. of the batterykey BK,'conducto'rs 5 and 6, the fuse 7, conductor 8 through the windingof the vibrator magnet VM, its interrupter contact 9, conductorslO and11, closed contact 12 of the key switch aassociated with the polechanger A, conductor 13, closed contact 14c of the key switch SK,conductor 15 to the other side of the battery B. The

circuit for vibrator magnet VM of the unit *ll of pole changer A may betraced from battery'B over the path just described to the branch overconductor 16, through the winding of the magnet VM, its interruptercontact 17, armature 71 conductor 11 to the other side of the battery Bover the previous described path.

The vibrator magnets W 13i and VM 0t nnits'l i and N of the pole changerA are energized over the circuits just described and due to theirinterrupter contacts 9 and 17 the armaturcs 70 and 71 of the saidnagconductor 2 closed contacts 5 3' nets VM and VM are vibrated. Thealternate closing of vibratory contacts and 51 of the vibrator magnet VMP81111113 impulses of current to flow through the windings 18 and 53 ofthe primary P of the transformer T, the circuit through the winding 18of the transformer 1 being traced from battery B over conductor 2,closed contacts 3 and at 01 the battery switching key BK, conductor 5 tothe point 1:), and extending from the point 19 over conductor :20, ftuse:21, winding 18 ot the primary- P of the transformer T, conductor 22,contact 23 off the pole changer switching relay PR, conductor 21, closedcontact and armature 7 0 of the vibrator magnet Viii -iondu'ctors and11, closed contact 12 of the switching key K, conductor 13 and closedcontact 1% of the starting key SK, coiuluctor to the other side ofbattery.

The circuit through the wii'niing 53 of the primary P of the transior 'lwhen contact 51 is closed may be that and L of battery switching keyBil, conductors and 20,-tuse 21, winding 53, conductor 54, normalcontact 55 of relay PR, conductor as, closed contact 51 and aruu-itnrtof magnet VM, conductors 10 and 11 to the other side of battery 13 overthe path described in connection with the circuit of wind ng 18. Theimpulses of current through the winding: 8 and 53 of the primary P 01"the transformer T which are induced into the secondary winding 32 of thesecondary S of the transformer T pass over conductors and 101 toconductors 33 and 3 1, through the wind-- ing of the alternating currentrelay AC, associated with the transformer T. The re tardation coil RC isprovided for tone purposes and has its primary winding 102 outacro'ssthe armature 70 and contact?) of the vibrator magnet VM thusplacing it in parallel connection with the sa-id magnet- VM. Oneterminal of the primary 102 is connected over conductor 103 throughnormal contact 104 of relay PR, conductor 105 to the armature 70 whichis connected to one side of battery The other side of the primary 102 isconnect-ed to the other side of battery B at contact 9 so that whenmagnet VM vibrates the opening and closing of contact 9 and armature 70will cause surges of current to flow through the primary 102 which areinduced into the secondary winding 106 which produce a tone which isdelivered over conductors 107 and 108 to the swiftcl'ibo'ard with whichpole changer A is associated, the tone being used for various purposesas is known in the art.

The vibrator magnet VM of the unit N 01" the pole changer A is vibratedby reason of its energizing circuit just described and the alternateclosing of its vibratory'contacts :32 and 31 permits impulses of currentLil) to flow through the windings 1S and 53 of the primary l. of thetranst'ormer T. The circuit through winding 18 being traced from batteryB to the point 19 and over conductor 26, i'use 2T, winding 18, conductor28, normal contact 29 of relay PR conductor 30, closed contact 31 andarmature 71 ot' the vibrator magnet TM, conductor 11 to the other sideof battery 13 over the path traced in connection with winding 18 ttransformer T. The circuit through the winding 55 ot the primary P oftransformer T of the unit N of pole changer A when contact is closed istraced from battery I to the point 19 and over conductor 26, fuse 2Twinding 53, conductor 57. normal contact 59 of relay PR condu. tor 58.closed contact and armature T1 of magnet Ysl, conductor 11 to the otherside oi battery B. The impulses of current through the windings 18 and53 ot the primary P of the trans former T are induced into the secondarywinding 32 ot the secondary S of the transformer T and pass overconductors (30 and 61 to conductors and 136, through the winding ofalternating current relay AC associated with the transformer T. Theretardation coil RC associated with the pole changer unit I? has itsprimary 102 also connected in parallel with the magnet YM acrossarmature (land cont-mt 1T operates in a manner similar to BC to delivera tone to the switchboard over conductors 110 and 111. Current overconductors 35 and 36 also passes through the alternating current relayAC associated with the unit N of the pole changer A.

The startin key switch SK is of the well known cam key type and whenmoved to its starting position SP to start the operation of the polechanger A, it is immediately moved to the right into its emergencyposition EP to close the spring contacts 2-37 and 38 for purposes aswill presently be described.

Relays AC and AC upon energizing close their alternate contacts 39 and10 to establish an energizing circuit for the emergency control relayEUR traced from battery B, conductor 2, closed contacts 3 and l of thebattery switching key BK, conductors 5 and a1 through the winding of therelay ECR conductor 12, alternate contact 39 of the alternating currentrelay AC, conductor alternate contact it) of the alternating currentrelay AC, conductors H and 15 to the other side of battery. The initialenergizing circuits or" the vibrator magnet VM and VM of the polechanger A were opened when starting key SK was moved from its startingposition SP to its emergency position EP but a substitute circuit is nowestablished tor the vibrator magnets VM and VM, the circuit of magnet VMbeing traced from battery B, conductor 2, closed contacts and 1 or thebattery key BK, conductors and (3, fuse T, conductor 8, through thewinding or the magnet YM, its interrupter contact 9, conductors 10 and11, closed contact 12 ot the key switch (4, associated with the polechanger A, ctmductor 15, normal contact t6 of the switching relay STY,conductor 1T, alternate contact 1 8 of the relay EUR, conductors 19, 50,it and 15 to the other side of battery B. The circuit for the vibratormagnet VM oi the pole changer (6 extends over conductor 16 through thewinding of the magnet VM, normal contact 1T, conductor 11 to the otherside of battery 13 over the path just described in connection with thevibrator magnet VM. The windings 18, and 1S of the primary windings 1"and P of the transtormers T and T receive current from battery B overcondu' tors 20 and 243 normal contacts and 55 of relay PE and normalcontacts 29 and 59 of relays PR, conductors and 5t, 28 and 57, cont-actsand 51 of magnet VM, contacts 31 and 52 of magnet V11, conductor 11 tothe other side ofbatt-ery 13 over the return path just traced inconnection with the magnets VM and VM.

The current from the winding 32 of the secondary S of the transformer Tpasses over conductors 100 and 101 to conductors and 34. which lead tothe switchboard with which the pole changer A is associated. The currentpassing over conductors 3B and 3-:l delivers a pre-determined cycle ofringing current to the switchboard. This current also flows through thealternating current AC and holds said relay energized as long as theunit X of the pole changer A is operated. The current from the winding32 of the se-ondary S of the transformer T which passes over conductors6t) and (31 to the conductors 35 and 36 which conductors lead to theswitchboard with which the pole changer A is associated to deliver apredetermined cycle of ringing current thereto. The current also passesthrough the wind mg of the alternate current relay AC. associated withthe unit N of the pole changer A and said relay AC remaining energizedas long as the unit N is operated.

Assuming that the primary pole changer A fails in its operation for thereason that the fuse 7 opens the vibrator magnets VM and VM of the polechanger, units M and N will receive no battery current from the batteryB. The vibrator magnets VM and VM of units M and N of the pole changer Aremain inert and the armatures and T1 of the vibrator magnets VM and VMcome to rest and the contacts 25 and 51 of the magnet VM, contacts 31and 52 of the magnet VM are open. The windings 18 and 53 of the primaryP of the transformer T and windings 18 and 53 01 the primary P of thetransformer T receive no current and therefore the alternating currentrelays AC and AC de-energize and restore to normal. The opening-ofalternate contacts 39 and LO of the relays AC and AC open the energizingcircuit of the relay ECR and the said relay EOE upon de-energizationpermits its normal contact i8 to close to establish an energizingcircuit for the switching relay SW, traced from battery 13, conductor 2,closed contacts and t of the battery BK, conductor 5, conductor 41through the winding of the relay SW, conductor 72, closed contacts 37and 38 of the starting key SK will be remembered that the starting keySK was moved to its emergency position to close thecontacts 37 and 38conductor 73-, normal contact 4-8 of the relay EGR. conductors 19, 50,44: and 15 to the other side of battery B). The switchingrelay SlV uponener-giz'ation, establishes a locking circuit for itself traced frombattery B, conductor 2,-closed contacts 3 and 4 of the key BK,conductors and 41 through the windingof the relay SW, conductor 72,closed contacts 37 and 38 of the key SK, conductor 73, alternate contactTet of the switching relay SV conductors 5O, 44 and to the other side ofbattery B. The switching relay SlV is now held energized independent ofthe contact 4-8 of the relay EGR. When the switching key SK was -movedtoits emergency position E]? to close its contacts 37 and 38, one portionof the .energizingcircuit of the vibrator magnets VM and VM of the units0 and P of the emergency pole changer C is closed, but due to the factthat normal contact 48 is open due to the fact that the relay ESE is inan energized condition while the pole changer A is in operation theenergizing circuits of the vibrator magnets Viv P and VM are held-open,but upon its de-energi- 'zatio'n, the relays EOE closes its contact 48,

establishing an energizing circuit for the vibrator ina-gusts V11 2 andVM ,cf the units 0 and P of the pole changer C which may be traced frombattery B, conductor 2, close contacts 3 mice of the battery BK,conductor 5, fuse 77 through the winding of the vibrator magnet VM ofthe unit- O of the pole changer C, interrupter cont-act 78-ofthe magnetVM conductors 79 and 80, conductorSl, closed contact 82 of the keyswitch a, conductors 83, 84 and 85, closed contact BS-of the switchingkey SK, conductor -73, normal contact 4-8 of the relay EUR, conductors49, 50, 4E'and 15 to the other-side ofbattery B. The circuit of thevibrator magnet VM of the unit P of the pole changer C is traced frombattery B, conductor 2, closed contacts 3 and 4C of key SK, conductor 5,fuse 77, conductor 86 through-the winding of the vibrator magnetfV-M,its interrupter contact 87, conboard with which the pole pole changer isin use.

ductor 80 to the other side of battery B over the path described inconnection with the vibrator VM The closure of normal contact 48 ofrelay ECE also establishes an energizing circuit for the pole changerswitching relays PR and PR, the circuitoi- EUR conductors i9 50. set and15 to the a a 1 r The circuit oi the other side of battery T. polechanger switching relay PR may traced from the point 19 over conductor26 through the winding of the relay Pit "and over conductor 89 to theother side 0t battery B as described in "connection with the relay PR.The relay PR upon energizetic-n closes its alternate contacts 23 and 55tofswitch the windings 18 and 53 of the primary P ot'the transformer Tfrom contacts and 51 of the vibrator magnet Viilof the pole changer A tothe vibratory contacts 92 and 93 of the vibrator magnet VH of the unit 0of the pole changer C, so that the vibrator VM which is now in vibratorycircuit due to the opening and closing of its interrupter contact 78,passes current through the windings 18 and 53 of the primary P or" thetransformer T. The relay PR upon energization closes its alternatecontacts 29 and 59 to disconnect windings 18"and of the primary P of'the transformer T from the contacts 31 and 52 of the vibr'ator magnetVM' of unit M, of

the pole changer A to the vibratory contacts 9% and'95 of the vibratormagnet Vlii of the "unit P of the pole changer C so that the windings 18and 53 of the primary P of the transformer T may receive current. Theinduced current from the primary P of the transformer T and the primaryP of the transformer T iiito the respective secondary windings 32 and 32of the transformers Tand T again permitsalternating current atpredetern'iin'ed cycles to pass over conductors 38, 3% and 35, 36 to theswitchchanger (J is associated. The closure of alternate contacts lOiand112 oi relays PH and PR switches the primaries 102 and 102 of theretardation coils RC and RC over conductor 113 and 114- in parallel withmagnets VM and VM to permit a tone to be generated for delivery to theswitchboard when Current also passes through the alternating currentrelays AC and AC "to again bring about their energization and theclosing'oi their alternate contacts 09 and 40 again establishes an licenergizing circuit for the relay ECR and relay ECR upon energizationopens its normal contact 4 8 but the opening 48 has no effect upon theenergizing circuits of the primary relays PR and PR and the vibratormagnets VM' and VM of pole changer C as switching relay SW is locked inits energized condition through its alternate contact 7 1 and thisalternate contact 74 also holds, as previously mentioned, relays PR andPR and magnets VM and VM energized.

Referring again to relay ECR which was de-energized when the relays ACand AG restore to normal, relay ECR upon de-energization closes itsnormal contact 115, and the conductors 116 and 117 which are connectedto the contact 115 have associated therewith, a suitable alarm signalwhich operates when the pole changer A stops operating to notify theattendant at the exchange so that the pole changer may be repaired. Fortesting the pole changers A and C, I provide test keys TK and TK, thetest key TK being associated with the pole changer A and the test key TKbeing associated with the pole changer C in the description. Havingassumed that the pole changer C has been automatically connected, shouldthe attendant wish to test the pole changer A, afterhaving taken care ofthe needed repair thereof, the test key TK may be operated to close anenergizing circuit for the vibrator magnets VM and VM of the units M andN of the pole changer A, the circuit being traced from battery B,conductor 2, closed contacts 3 and 1, conductors 5 and 6, fuse 7 throughthe winding of the magnet VM, interrupter contact 9, conductors 10 and11, closed contacts 118 and 119 of the test key TK, conductors 120 andto the other side of battery, The circuit of the vibrator VM is t 'acedover conductor 16 through the winding of the magnet VM, its interruptercontact 17 conductor 11 to the other side of battery, and vibratormagnets VM and VM' now operate over this circuit.

Assuming that the fuse 21 or 27 opens, this will open the batterycircuit through either the windings 18 and of the primary P andtransformer T, or the wind lugs 18 and 53 of the primary P of thetransformer T, and as no further current passes through either of thewindings P or P, as the case may be, the relay AC or the relay AC willbe ole-energized. and the opening of either alternate contact 39 or 40will bring about the operation of the circuit as already described inconnection with the opening of the fuse 7.

I also provide a switching position 0 for the key K which position isassociated with the operative circuit of the pole changer O and assumingthat neither pole changer is operating and one desires to con ncct thepoie changer C, the key K is moved to its position 0 to close contactslei-O and 123 and operates starting key SK to close its starting contact14-, key SK is moved to its starting position SP to close the initialenergining circuit of the vibrator magnets VM and V1? from battery Bconductor 2 closed contacts 3 and a, conductor 5, fuse 77, winding ofthe magnet VM' interrupter contact '78 of the magnet VM'- conductors 79and 30, closed contact 1&0 of conductor 121, conductor 13, closedcontact 1% of key SK, conductor 15, to the other side of battery B. Thecircuit of the vibrator magnet- PM extends over conductor 86 through thewinding of M interrupter contact 87, con.- ductor 80 to the other sideof battery. En. ergizing circuits for pole changer switclr ing relays PRand PR are also establishml the circuit of PR being traced from batteryB, conductor 2, closed contacts 3 and a, conductors 5 and 20, windingPR, conductors 0'8 and 89, normal contact 90 of key TR, conductor 80,closed contact 110, conductors 121 and 123, closed contact lei, of keySK, conductor 15, to the other side of battery B. Relays PR and PR closetheir alternate contacts 23 and 55, and 29 and 59 to connect the primarywindings P and P of the transformers 'l and T in connect-ion with thecontacts 92 and 93 of the vibrator magnet VM and contacts 9% and 95 ofthe vibrator magnet VM Ringing current is now delivered to conductors 33and 3 1 from transformer T at a predetermined cyle to the switchboardand to conductors and 36 from the transformer T at a pro-determinedcycle to the switchboard. Relays AG and AG and ECR are operated aspreviously described. The key SK is now moved from its starting positionSP to its emergency position EP, and closed contact 14 of the key SK isopened and substitute circuits for the magnets VH and VM and relays PRand PR are now closed and extend over conductors 121 and 45, normalcontact as, of relay SXV conductor 17, alternate contact 18 of relayECR, conductors 49, 50, and 15 to the other side of battery B, and theoperation of the apparatus when pole changer C is operating from thispoint is readily apparent from the previous description.

Should pole changer Gst-op due to the opening of the fuse 77, thecircuits of the vibrator magnets VM and VM would reopen and thealternating current relays 1C and AC and relay ECR will be de-energizedand the'closure of normal contact &8 of the relay EGR will establish anenergizing circuit for the vibrator and magnets VM and VM of the polechanger A over a circuit traced from battery B, conductor 2, closedcontacts 3 and t conductors 5 and.

6, fuse 7, through the windings of vibrator magnets VM and VM' theinterrupter contacts 9 and 17 of the magnets VM and VM, over conductor11, conductor 122, alternate contact 123 of the key K, conductor 84,conductor 85, alternate contact 38, conductor 73, normal contact 48,conductors 49, 50, H and to the other side of battery B.

The closure of normal contact 48 of the relay ECR establishes anenergizing circuit for the switching relay Sil over a circuitaspreviously described, and the opening of its normal contact 46 opens thecircuits of the pole changer switching relays PR and PR. The closurealternate contact 7st of the relay SlV established a locking circuit foritself, as already described. The vibrator magnets VM and VM now operateand current through the primary windings P and P of the transformers Tand "l" again delivering a predetermined cycle. of current to theconductors 34c and 35 connected 'to the transformer T, and conductors 3aand 35 which are connected to the transformer T. Relays AC and AC areagain energized'as is also the relay ECR and the opening of normalcontact as of relay ECR opens the initial energizing circuits of themagnets VM and VM, but as alternate contact 74 of relay SW is closed,the magnets VM and VM are energized through this contact independent ofthe contact 48.

Wit-h the switching system or" my invention it is readily apparent thateither pole changer A or C may be used by simply moving the key K toeither its a'or 0 posi- 'tion and that should either pole changer stopfunctioning for any reason depending on which one is operatingat thetime automatic means are provided for instantly switching "to the idlepol'e'changer without any manipulation of keys or buttons thuseliminatingan interruption of the ringing current to the switchboardwith which the p'olechangers are associated.

TV-hile I have illustrated and described aprefer'red embodiment ofmyinvention, I do notwish to be limited "to this articular application ofmy invention as it may be Yused for a number'of purposes.

hat I claim as new and desire to secure by United States Letters Patent,is as followsz- '1. A switching system oi the character describedincluding a pair of pole changers, each of which comprises two units, akey for rnani 1ailly controlling the connection of either pole cha ger,a switch for startin the operation GfSiLlCl pole c'hanger and con tr'olmeans 00nd tinned by "said as; and operating "automaticallyl to switchfrom one pole changer {to "the-other.

' '2. A switching system of the character described including a pair ofpole changers a They :for manually =congiecti each of which coniorisestwo units, a "keyfor manually controlling the connect-ion'o-t eitherpole changer, a s rite-h common to said pole changers for starting thepole changer connected by said key, said switch having an emergencyposition to which emergency position it moved from its starting positionand control means conditioned by the movement of said switch to saidemergency position ,to automatically switch from the pole changer in useto the other pole changer.

3. A switching system of the character described comprising 7 a pair ofpole changers, a key for manually controlling the connection of eitherpole changer, a switch having a starting position and an emergencyposition, starting means i or said pole changer connected by said key w7 said switch is moved to starting. posit n, and conditioning :meanscontrolled lay said switch when moved from said starting 2P0- si'tion tosaid emergency position to switch from one pole changer to'athe otherpole changer when the pole changer in use is disabled.

l. A switching system of the character described including apair-of polechangers each -'comprising two units, a :key f g neeting either polechanger lit, a switch for starting said pole changer cionn'e'c'ted bysaid hey, an emergency position for said switch to which itis moved fromstarting position, a pair of transformers common to said pole changers,and means controlled by said switch when in emergency position to switchthe transformers from one pole changer to the other.

A switching system of the character described including a pair of polechangers, a key 'iior manually connecting either pole changer incircuit, a switch having a starting position tor starting said polechanger connected by said hey, an emergency position for said switch towhich it is moved frol-n its starting position, a pair of transformerscommon to said pole changers, a pair of relays common to said t"dormers, and means controlled by said switch when :in' emergencyposition to cause the operation of said relay-s -whe nthe pole changerin =use is'disabled toaaultomat allyswitch said transformers trom thesaid pole changer to theiother pole changer.'

6. A sWitclring-syste n of the character described including a pairoi'po'le changers,

ither pole changer in circuit, a switch having {{1- start ing.jposition'for starting said pole changer connected by iid keyfatinn "tor said *siitch to at from -:its"sta1 in'g *posi on, ffionners @011 n E t 1 op'airoimel'ay oom 113}; to said a 1 t energized by current fromtrasiormers when the pole changer in use is operatin and meanscontrolled by said relays for automatically switching the transformersfrom the pole changer in use to the second pole changer in case thefirst said pole changer is disabled.

7. A svitching system of the character described including a pair ofpole changers, a key for manually connecting either pole changer, aswitch for starting said pole changer connected by said key, anemergency position for said switch to which it is moved from itsstarting position, a pair of transformers common to said pole changers,a pair of relays common to said transformers energized by current fromsaid transformers, a pair of relays common to said pole changers, andmeans controlled by said first pair of relays and the switch inemergency position to operate said second pair of relays to switch saidtransformers from the pole changer in use to the second pole changer.

8. A switching system of the character described including a pair ofpole changers, a key for manually connecting either pole changer, aswitch for starting said pole changer connected by said key, anemergency position for said switch to which it is moved from itsstarting position, a pair of transformers common to said pole changers,a pair of relays common to said transformers and energized by currentfrom said transformers, a pair of relays common to said pole changers, arelay controlled by said first pair of relays, switching meanscontrolled by said first pair of relays when the pole changer in use isdisabled to effect said relay to operate said second pair of relays toswitch said transformers from the disabled t'ansformer to the secondtransformer.

9. A system including a pair of ringing current supply devices, a keyfor connecting either of said current supply devices, a supply circuit,and a switch for conditioning automatic means for disassociating one ofsaid devices in use from said supply circuit and for connecting theother one thereto.

Signed by me at Chicago, in the county of Cook and State of Illinois,this 28 day of Sept, 1923.

JOHN F. MEYERS.

